Production of needle coke from coal for pitch

ABSTRACT

Process for producing graphitizable needle coke be delayed coking of a nonpetroleum fraction having a high content of condensed ring aromatic compounds and lower and upper cut points within the range from about 600* F. to about 1,200* F. In a preferred embodiment, the hereinabove noted fraction is separated from coal tar pitch having components boiling above 1,000* F. and the fraction boiling above 1,000* F. coked to carbon electrode grade coke.

United States Patent [72] Inventor Ward J. Bloomer Westfield, NJ. [2]]Appl. No. 827,603 [22] Filed May 26, 1969 [45] Patented Nov. 2, 1971[73] Assignee The Lummus Company Bloomfield, NJ.

[54] PRODUCTION OF NEEDLE COKE FROM COAL FOR PITCH 13 Claims, 2 DrawingFigs.

[52] U.S.Cl 208/131, 208/8, 208/80, 208/81, 208/82, 208/83, 208/93 [51]1nt.Cl Cl0g 9/14 [50] Field of Search 208/81-83, 46,106, 127,131, 8, 44,45; 201/25; 260/675 [56] Relerences Cited UNITED STATES PATENTS2,795,538 6/1957 Ratte et a1. 260/675 3,331,853 7/1967 Halden 260/6753,407,209 10/1968 260/675 3,440,163 4/1969 208/127 2,901,416 8/1959208/83 2,905,623 9/1959 208/83 2,922,755 1/1960 Hackley 208/1063,035,989 5/1962 Mitchell 201/17 3,338,817 8/1967 Zrinscak et a1. 208/463,116,231 12/1963 Adce 208/46 3,035,308 5/1962 Ragoss et a1. 208/45Primary Examiner-Herbert Levine Attorney-Marn & Jangarathis ABSTRACT:Process for producing graphitizable needle coke be delayed coking of anonpetroleum fraction having a high content of condensed ring aromaticcompounds and lower and upper cut points within the range from about 600F. to about 1,200" F. In a preferred embodiment, the hereinabove notedfraction is separated from coal tar pitch having components boilingabove 1,000 F. and the fraction boiling above 1,000" F. coked to carbonelectrode grade coke.

Gal

Distillate Gus PATENTEnnnv 2 l97l 3. 6 l 7, 515

' SHEET 1 [1F 2 Compression Fig.

INVI'JN'I'OR.

Q BY

ATTORNEYS Ward J. Bloomer PATENTEDNUV, 2

-W0rd J. Bloomer ATTORNEYS PRODUCTION OF NEEDLE COKE FROM COAL FOR PITCHThis invention relates to the production of graphitizable needle cokeand more particularly to a process for the simultaneous production ofsuch needle coke and carbon electrode grade coke.

Needle coke, after calcination and graphitization, is characterized by alow longitudinal coefl'icient of thermal expansion which is matched by alow electric resistivity and it is primarily used in producinghigh-quality synthetic graphite electrodes for electrosteel furnaces andfor other electrothermal and chlor-alkali industries. Needle coke is apremium grade coke which is generally priced at $50$ 100 per ton.

ln copending application Ser. No. 746,706 filed of July 15, 1968 thereis described a process for producing a carbon electrode grade coke froma particular feedstock having a high content of condensed aromaticcompounds. Carbon electrode grade coke is generally priced at $-$40 perton and consequently the production of needle coke from such a feed ismore desirable. 1

Accordingly, an object of this invention is to provide a new andimproved process for producing graphitizable needle coke.

Another object of this invention is to provide a process for thesimultaneous production of such needle coke and carbon electrode gradecoke.

A further object of this invention is to provide a process for producingsuch needle coke by a delayed coking technique.

Still another object of this invention is to provide a process forproducing such needle coke from a feed having a high content ofcondensed ring aromatic compounds.

These and other objects of the invention should be more readily apparentfrom the following detailed description thereof when read with referenceto the accompanying drawing wherein:

FIG. 1 is a simplified schematic flow diagram of an embodiment of theinvention; and

FIG. 2 is a simplified schematic flow diagram of another embodiment ofthe invention.

The objects of this invention are broadly accomplished by subjecting tocoking conditions of temperature and pressure a fraction derived from anonpetroleum source having a high content of condensed ring aromaticcompounds and at least 80 percent of which boils within the range fromabout 600 F. to about l,200 F., preferably from about 600 F to aboutl,000 F., to produce graphitizable needle coke. ln accordance with apreferred embodiment of the invention, the fraction boiling within therange from about 600 F. to about l,200 F. is derived from a feedstockwhich includes components boiling above l,200 F. and the residue, afterseparation of the fraction used as a source of such needle coke, isemployed for the production of .a carbon electrode grade coke.

The feeds generally treated in accordance with the invention are derivedfrom coal and contain a fraction having a high content; i.e., generallygreater than about 70 percent, of condensed ring (polynuclear) aromaticcompounds, both heterocyclic and isocyclic. The feed is preferablytreated to recover a fraction having upper and lower cut points fallingwithin the range from about 600 F. to about l ,200 F. and this fractionis coked to a high-grade needle coke, with the higher boiling residue;i.e., the fraction boiling above the upper cut point of the needle cokefraction, preferably being coked to carbon electrode grade coke. it isto be understood that the fraction employed for the production of needlecoke may have components boiling throughout the 600 F. to L200" F. rangeor components boiling through only a portion of the range; i.e., 700900F. It is further to be understood that components boiling below about600 F. are only excluded for the reason that such components are notcoke precursors and therefore would not he "coked" during the operation.Consequently, if desired, components boiling below about 600 F. may beineluded lit! a diluent, but in general such components are excluded inthat they would diminish the overall capacity of the equipment. Apreferred feed is a coal tar pitch obtained by either thehigh-temperature or low-temperature carbonization of coal, as generallyknown in the art, the former feed particularly being generallycharacterized as completely comprised of condensed ring aromaticcompounds (an estimated 5,000 of such compounds), with two-thirds of thearomatic compounds being isocyclic and the remaining third heterocyclic.

The feed to be converted to needle coke, as hereinabove noted, may alsocontain components which boil above about l,200 F., but higher boilingcomponents should not comprise more than about 20 percent of the feed tobe coked to needle coke, preferably no greater than about 15 percent ofthe feed. The coking of a feed containing components boiling above aboutl,200 F. produces a grade of needle coke which is lower than the gradeof needle coke produced from a feed free of such components, but thislower grade of needle coke has a coefficient of thermal expansionsufficiently low to meet various commercial specifications for a needlecoke.

The invention will now be further described with respect to theaccompanying drawings which illustrate embodiments for delayed coking ofa feed containing coal tar pitch. The drawing has been simplified tofacilitate the description thereof and therefore various processingexpedients generally employed in the art are not specifically showntherein. It is to be understood that the embodiment of the drawings areonly illustrative of the invention and therefore the scope thereof isnot to be limited thereby. Thus, for example, although the embodimentsare particularly directed to the use of vacuum distillation equipmentfor recovering a 600-l ,000 F. fraction for the production of needlecoke, it is to be understood that fractions having other boiling rangesor fractions obtained in a manner other than by vacuum distillation;e.g., solvent extraction are within the spirit and scope of theinvention.

Referring now to FIG. 1, a feed, such as soft coal tar pitch derivedfrom the higher temperature carbonization of coal, in line 10 is passedthrough a heater 11 to effect heating thereof to the operatingtemperature of a vacuum flash tower, as hereinafter described. Theheated feed from heater ll in line 12 is introduced into a vacuum flashtower 13, operating at a temperature and pressure designed to recoverfrom the feed an overhead fraction containing components having boilingpoints up to about l,000 F.; the tower 13 generally being operated at atemperature from about 700 F. to about 850 F. and a pressure from about0.25 p.s.i.a. to about 2.0 p.s.i.a.

An overhead is withdrawn from flash tower 13 through line 14, compressedto atmospheric pressure in a suitable compression device 15, preferablya multistage vacuum ejector and passed through cooler 16 wherein thevapor is cooled to a temperature at which the vapor is condensed,generally a temperature from about 300 F. to about 500 F. The cooledliquid from cooler 16 in lines 17A and B is introduced above and below,respectively, the vapor-liquid contact decks of a combinationfractionator l8 operated under temperature and pressure conditions toproduce a heavy oil bottoms having a lower cut point of about 600 F. andan upper cut point between about 900 F.; and about 1,000 F.; a lightoil, generally having cut points between about 400 F. and about 600 F.;and an overhead vapor comprised of gas and distillate, generally boilingup to about 400 F. The fractionator 18 is also provided with coke drumoverhead vapors through lines 19 and 20 and heavy oil recycle throughlines 53 and 54, as hereinafter described. The fractionator 18 isgenerally operated at an overhead temperature between about 300 F. andabout 400 F., a bottoms temperature of between about 650 F. and about850 F. a pressure between about 25 p.s.i.g. and about p.s.i.g. and avolumetric recycle ratio of from about 0.3:1 to about 20:], preferablyfrom about 0.5:l to about 2.0:l, based upon equivalent feed tofractionator 18, with higher recycle ratios generally decreasing theoverall capacity of the equipment. A portion of the liquid from cooler16 may be passed through branch line 17C to storage and/or furthertreatment; e.g., to produce carbon black.

A heavy oil bottoms having the hereinabove noted cut points is withdrawnfrom fractionator 18 through line 21 and a portion thereof is passedthrough line 22 to a coking heater 23 operated at an outlet temperatureof between about 900 F.- and about l,000 F. and in a manner to preventpremature coking therein; i.e., the feed is maintained in turbulentmotion or at a high velocity by providing temperature and pressureprofiles in the heater that will produce partial vaporization of thefeed, thereby preventing the coking problems caused by slow moving feedin the liquid state. In addition, controlled amounts of steam may byintroduced into the coking heater 23 at appropriate places to obtain therequired turbulence or high velocity.

The heated heavy oil is withdrawn from the coking heater 23 through line24 and introduced into coke drums 25, of a type known in the art,wherein the heavy oil is converted to needle coke and lightercomponents. The coking drums are operated at a pressure of between aboutp.s.i.g. and about 90 p.s.i.g., preferably between about 25 and about 90p.s.i.g. and an overhead temperature of between about 840 F. and about900 F., preferably between about 860 F. and about 900 F. The needle cokeis withdrawn from the drums 25 through line 26.

An overhead is withdrawn from the coke drums 25 through line 19 andintroduced into the fractionator 18 at a point below the introduction ofthe flashed overhead in line 17A. The cooled flashed overhead in line17A aids in condensing heavy oil from the coke drum overhead vapor.

A bottoms recovered from the flash tower 13 in line 31, having aninitial boiling point of greater than 900 F. to l,000 F., is mixed witheither heavy oil from the fractionator 18 in line 32, light oil from thefractionator in line 33 or both to dilute the high boiling bottoms. Thelight oil and/or heavy oil is mixed with thebottoms in an amount toprovide a volumetric ratio of between about 0.2 and about 0.5 of lightand/or heavy oil to bottoms. The remainder of the light oil is passedthrough line 33A to storage and/or further treatment.

The mixture is introduced into a coking heater 35, of a type known inthe art. The coking heater is operated so as to produce an outlettemperature of between about 900 F. and about 960 F. The coking heater35 is operated as generally known in the art to prevent premature cokingtherein, i.e., the feed is maintained in turbulent motion or at a highvelocity by providing temperature and pressure profiles in the heaterthat will produce partial vaporization of the feed, thereby preventingthe coking problems caused by slow moving feed in the liquid state. Inaddition, controlled amounts of steam may be introduced into the cokingheater 35 at appropriate places to obtain the required turbulence orhigh velocity.

The heated mixture is withdrawn from the coking heater 35 through line36 and introduced into coke drums 37, of a type known in the art,wherein the mixture is converted to carbon electrode grade coke andlighter components. The coking drums are operated at a pressure ofbetween about 15 p.s.i.g. and about 90 p.s.i.g., preferably betweenabout 25 and about 90 p.s.i.g. and an overhead temperature of betweenabout 840 F. and about 900 F. preferably between about 860 F. and about900 F. The coke is withdrawn from the drums 37 through line 38.

An overhead is withdrawn from the coke drums 37 through line andintroduced into the fractionator 18 at a point below the introduction ofthe flashed overhead in line 17A. The cooled flashed overhead in line17A aids in condensing heavy oil from the coke drum overhead vapor. Aportion of the heavy oil withdrawn from fractionator 18 through-line 21is passed through line 50, cooled in heat exchanger 51 by indirect heattransfer with a suitable coolant; e.g., the feed to the flash tower 13in line 10, and further cooled by indirect heat transfer with a suitablecoolant; e.g., boiler feed water, in heat exchanger 52 to a temperaturesuitable for inducing additional recycle in fractionator 18 to meet thehereinabove noted volumetric recycle requirements, generally atemperature from about 400 F. to about 700 F. A portion of the cooledheavy oil from heat exchanger 52 is introduced into the fractionator 18through line 53 to aid in providing the recycle requirements. Thus, thetotal recycle is comprised of: the heavy oil fraction returned throughline 53 and the condensed portion of the coke drum overhead vaporsintroduced through lines 19 and 20, with the condensation of materialsfrom the coke drum overhead vapors being induced by direct contact infractionator 18 between the coke drum overhead vapors and both thecooled liquid introduced through line 17A and the cooled heavy oilrecycle introduced through line 53. The remaining heavy oil from heatexchanger 52 is introduced into the fractionator 18 through line 54 tomaintain desired operating conditions and passed through line 55 tostorage and/or further treatment; e.g., the production of carbon black.

A further embodiment of the invention is illustrated in FIG. 2.Referring now to FIG. 2, a liquid feed, such as, soft coal tar pitchderived from the highor low-temperature carbonization of coal, in linegenerally at a temperature between about 400 F. and about 600 F. isintroduced into a coker combination fractionator 101 operated undertemperature and pressure conditions to produce a heavy oil having alower cut point of about 600 F and an upper cut point between about 700F. and about 1,000 F.; light oil, generally having cut points betweenabout 400 F. and about 600 F.; and an overhead vapor comprised ofgas anddistillate, generally boiling up to about 400 F. The fractionator 101 isgenerally operated at an overhead temperature of between about 300 F.and about 400 F., a pressure between about 25 p.s.i.g. and about 100p.s.i.g., and a volumetric recycle ratio from about 0.3:1 to about2.0:l, preferably from about 0.5:] to about 2.0: 1, based on equivalentfeed, with higher recycle ratios generally decreasing the overallcapacity of the equipment.

The liquid feed introduced into the fractionator 10! through line 100 iscontacted with hot coke drum overhead vapors introduced through lines102 and 103, obtained as hereinafter described, resulting in flashing ofmaterials having boiling points up to about 900 F. to about l,000 F.from the liquid feed. The unflashed portion of the liquid feed iswithdrawn from the fractionator 101 through line 104 and if the heatinput to the fractionator 101 is not sufficient to flash essentially allof the material boiling up to about 900 F. to about l,000 F. from thefeed, the portion of the liquid in line 104 is introduced into a flashtower 105 through line 106, operating at a temperature and pressure toprovide an overhead containing components boiling up to about l,000 F.;generally an operating temperature of between about 600 F. and about 800F. and an operating pressure between about 0.25 p.s.i.a. and about 2.0p.s.i.a. An overhead is withdrawn from flash tower 105 through line 107compressed to atmospheric pressure in a suitable compression device 108,preferably a multistage vacuum ejector, and passed through cooler 109wherein vapor is cooled to a temperature at which the vapor iscondensed, generally a temperature from about 200 F. to about 400 F. Thecooled liquid from cooler 109 in line 110 is mixed with heavy oil inline 112 withdrawn from the combination-fractionator 101, as hereinafterdescribed and the mixture introduced into a coking heater 113, of a typeknown in the art. The coking heater 113 is operated at an outlettemperature of between about 900 F. and about l,000 F. and in a mannerto prevent premature coking therein; i.e., the feed is maintained inturbulent motion or at a high velocity by providing temperature andpressure profiles in the heater that will produce partial vaporizationof the feed, thereby preventing the coking problems caused by slowmoving feed in the liquid state. In addition, controlled amounts ofsteam may be introduced into the coking heater 113 at appropriate placesto obtain the required turbulence or high velocity.

The heated heavy oil is withdrawn from the coking heater 113 throughline 114 and introduced into coke drums 115, of a type known in the art,wherein the heavy oil is converted to graphitizable needle coke andlighter components. The coking drums are operated at a pressure ofbetween about 15 p.s.i.g. and about 90 p.s.i.g., preferably betweenabout 25 and about 90 p.s.i.g. and an overhead temperature of betweenabout 840 F. and about 900 F., preferabiy between about 860 F. and about900 F. The needle coke is withdrawn from the drums 115 through line 116.

An overhead is withdrawn from the coke drums 115 through line 103 andintroduced into the fractionator 101 below the point of introduction ofthe feed in line 100 to recover various components from the overhead;the overhead also providing a portion of the heat requirements forflashing of the feed.

A bottoms recovered from the flash tower 105 in line 121 or the bottomsin line 104, having an initial boiling point of greater than 900 F. tol,000 F., is mixed with either heavy oil from the fractionator 101 inline 122, light oil from the fractionator 101 in line 123 or both, todilute the high boiling bottoms. The light oil and/or heavy oil is mixedwith the bottoms in an amount to provide a volumetric ratio of betweenabout 0.2 and about 1.0 of light and/or heavy oil to bottoms. Theremainder of the light oil is passed through line 123A to storage and/orfurther treatment.

The mixture in line 124 is introduced into a coking heater 125, of atype known in the art. The coking heater is operated so as to produce anoutlet temperature of between about 900 F. and about 960 F. The cokingheater 125 is operated as generally known in the art to preventpremature coking therein; i.e., the feed is maintained in turbulentmotion or at a high velocity by providing temperature and pressureprofiles in the heater that will produce partial vaporization of thefeed, thereby preventing the coking problems caused by slow moving feedin the liquid state. In addition, controlled amounts of steam may beintroduced into the coking heater 125 at ap-' propriate places to obtainthe required turbulence or high velocity.

The heated mixture is withdrawn from the coking heater 125 through line126 and introduced into coke drums 127, of a type known in the art,wherein the mixture is converted to carbon electrode grade coke andlighter components. The coking drums are operated at a pressure ofbetween about p.s.i.g. and about 90 p.s.i.g., preferably between about25 and about 90 p.s.i.g. and an overhead temperature of between about840 F. and about 900 F., preferably between about 860 F. and about 900F. The coke is withdrawn from the drums 127 through line 128.

An overhead is withdrawn from the coke drums 128 through line 102 andintroduced into the fractionator 101 below the point of introduction ofthe feed in line 100 to recover various components from the overhead;the overhead also providing a portion of the heat requirements forflashing of the feed.

A heavy oil fraction, having the hereinabove noted cut points, iswithdrawn from fractionator 101 through line 150, cooled in heatexchanger 151 by indirect heat transfer with a suitable coolant; e.g.,the feed in line 100, and further cooled by indirect heat transfer witha suitable coolant; e.g., boiler feed water, in heat exchanger 152 to atemperature suitable for inducing required recycle in fractionator 101,generally a temperature of from about 400 F. to about 700 F. A portionof the cooled heavy oil is passed through line 153 to provide the heavyoil for lines 112 and 122, as hereinabove described.

Another portion of the heavy oil from heat exchanger 152 is introducedinto the fractionator 101 through line 156 at a rate to provide thehereinabovedescribed volumetric recycle ratio. Thus, the total recycleis comprised of the heavy oil fraction returned through line 154 and thecondensed portion of the coke drum overhead vapors introduced throughlines 102 and 103, the condensation being induced by direct contact withthe cooled heavy oil fraction. The remaining portion of the heavy oilfraction from heat exchanger 152 is introduced into the fractionator 101through line 155 to maintain desired operating conditions and passedthrough line 156 to storage and/or further treatment; e.g., productionof high-grade carbon black as a result of its high BMCI, or recognizedaromatic factor and its low sulfur content.

Numerous modifications of the hereinabove-described embodiments arepossible within the scope of the invention. Thus, for example, needlecoke may be produced from the 600 F. to l,000 F. fraction without thesimultaneous production of carbon electrode grade coke from the l,000 F.fraction. As another modification, a separate combination fractionatormay be employed for each coking operation instead of the singlefractionator as employed in the embodiments illustrated in FIGS. 1 and2. The use of a second fractionator may be advantageous in someoperations in that the needle coke producing drums may then be operatedat a higher pressure than the carbon electrode coke drums, withoutnecessitating throttling of vapors.

As a further modification a portion of'the coke drum overhead vapors maybe used to assist the flashing in tower 13, such overhead vapors beingpassed to the fractionator through line 14 in admixture with thefraction flashed from the feed.

As yet a further modification, the embodiment of FIG. 2 may be operatedin accordance with the process described in US. application Ser. No.746,706, with the heavy oil recovered from the combination fractionatorbeing employed for the production of graphitizable needle coke. Thisprocedure is less preferred in that needle coke production is reduced inthat the graphitizable needle coke precursors are not effectivelyrecovered in the combination-fractionator.

As still another modification, the flash towers 113 and 105 of theembodiments of FIGS. 1 and 2, respectively, may be operated asconventional multijet induced vacuum flash towers with the overheadvapors being condensed for tower total reflux return and employed inlines 17 and 110, respectively, as hereinabove-described.

As yet a further modification, the embodiments of FIGS. 1 and 2 may beoperated in a manner whereby the feed to the needle coke producing drumscontains components boiling above about l,200 F., the components boilingabove about l,200 F. comprising no more than about 20 percent of thefeed to the needle coke drums, generally from about 5 to about '15percent of the feed. Thus, for example, in accordance with theembodiment of FIG. 1, the heavy oil bottoms in line 22 may be mixed witha portion of coal tar pitch feed stock form line 10 in line 10a toprovide components boiling above about l,200 F. The coal tar pitch isemployed in line 10a in an amount whereby the total feed introduced intoheater 23, as hereinabove noted, contains no more than about 20 percentof components boiling above about 1,200 F. It is to be understood,however, that the coal tar pitch in line may be mixed with the heavy oilin line 22 in proportions greater than 20 percent in that the coal tarpitch also contains components boiling below l,200 F. and therefore suchgreater amounts will not provide more than 20 percent of componentsboiling above l,200 F. Similarly, in accordance with the embodiment ofFIG. 2, coal tar pitch may be added to the feed to the heater 113 in themanner hereinabove described.

These and other modifications should be apparent to those skilled in theart from the teachings herein.

The invention is further illustrated by the following examples but thescope of the invention is not to be limited thereby.

EXAMPLE I A coal tar pitch is vacuum distilled into two fractions asdescribed in table i.

The distillate and residue were each coked in a single pass atmosphericoperation at a temperature of 840-870 F., with the coke produced fromthe distillate being a graphitizable needle coke having a lowlongitudinal coefficient of thermal expansion of not substantially aboveabout 6.0Xl" (C.) and the coke produced from the residue having acoefficient of thermal expansion in the range of l2-20Xl0" (C.)", beingcharacterized as carbon electrode grade coke. The dual coking operationproduced parts of the needle coke and 36 parts of the carbon electrodegrade coke, per 100 parts of whole coal tar pitch.

The coking of the pitch, without the dual coking of the invention,produces about 56 parts of carbon electrode grade coke per 100 parts ofpitch.

EXAMPLE ll TABLE 2 Inspections of Pitch Specific gravity, I00 F.l60 F.l.2234 Viscosity,

SFS at 2l0 F. Softening PL, 'F. Conradson Carbon Residue, Wt. I: Ash,W11 b Sulfur, Wt. 17

TABLE 3 Delayed Coking Product Yield: on Pitch On Coker Charge Tar LightOil Carbolic Oil Naphthalene Oil Wash Oil Heavy Oil Coke, CarbonElectrode, Amorphous Coke 52.3

TOTAL 100.0

The heavy oil, is further distilled to an initial 650 F. cut point andthis distilled fraction coked in a single pass atmospheric operation ata temperature of 840-870 F. to produce the following products:

TABLE 4 Delayed Coking Yields On Cokcr of 650 F. Distillate Charge OnPitch Gas L8 0.6 Distillate 76.l 23.8 Coke, Graphite ElectrodeGrade'Needle Coke 22.l 6.9 TOTAL l00.0 3L3 The coke produced has thefollowing properties:

TABLE 5 Carbon electrode Graphite electrode Grade-Amorphous GradeNeedleCoke Coke Yield, Wt. 11 on Coal Tar Pitch 52.3 6.9 Proximate AnalysisMoisture, Wt. I; 041 0.l0 Volatile Matter, Wt. k 8.7 5.6 Fixed Carbon,Wt. '17 9L3 94.2 Ash, Wt. I; nil 0J8 Sulfur, Wt. I: 0.2 0.2 Bulkdensity, lb.lcu. ft. 60.4 757 Thus, 100 parts of pitch produces 52.3parts of carbon electrode grade coke and 6.9 parts of graphitizableneedle coke and the yield of needle coke may be increased by operatingthe combination-fractionator to recover more such needle coke precursorsfrom the initial coal tar pitch feed.

The overall process of the present invention is an improvement over theprocess of copending application Ser. No. 746,706 in that a feedstockhaving a high content of condensed ring aromatic compounds is upgradedto a coke commonly referred to as graphitizable needle coke, which aftercalcination and graphitization has a longitudinal coefficient of thermalexpansion/C. not substantially above about 6.0Xl0", rather than solelyto carbon electrode grade coke. in addition, the process of theinvention incorporates the advantages inherent in an effective coking ofa feedstock having a high content of condensed ring aromatic compounds,as noted in said copending application; i.e., high coke yields and thelike.

Numerous modifications and variations of the invention are possible inlight of the above teachings and therefore the invention may bepracticed otherwise than as particularly described.

What is claimed is:

l. A delayed coking process for producing graphitizable needle coke froma feed containing coal tar pitch, comprising:

separating from a feed containing coal tar pitch a fraction having atleast about percent of the components thereof boiling somewhere withinthe range from about 600 F. to about l,200 F. said fraction having ahigh content of a mixture of condensed ring aromatic compounds; rapidlyheating said fraction to delayed coking temperature; and subjecting saidfraction to delayed coking to produce graphitizable needle coke.

2. The process as defined in claim 1 wherein the upper and lower cutpoints of the fraction fall within the range from about 600 F. to aboutl,200 F.

3. The process as defined in claim 1 wherein the upper and lower cutpoints of the fraction fall within the range from about 600 F. to about1,000 F.

4. The process as defined in claim 1 wherein said coking is effected ina coke drum operating at an overhead temperature between about 840 F.and about 900 F.

5. The process as defined in claim 4 wherein said coke drum is operatedat a pressure from about 15 to about p.s.i.g.

6. A delayed coking process for producing graphitizable needle coke froma feed containing coal tar pitch, comprising:

a. introducing a feed containing coal tar pitch into a separation zonewherein a fraction having a boiling point of no greater than about l,000F. is separated from the feed,

said fraction having a high content of condensed ring aromaticcompounds;

b. introducing the fraction into a fractionation zone operated underconditions to produce a bottoms having upper and lower cut points withinthe range from about 600 F. to about l,000 F.;

c. passing at least a portion of the bottoms through a heater to effectheating thereof to a temperature from about 900 F. to about 1,000 F.;

d. introducing the heated bottoms into a coking drum to effect delayedcoking thereof at a temperature from about 840 F. to about 900 F. tographitizable needle coke; and

e. passing overhead vapors from the coking drum to the fractionationzone.

7. The process as defined in claim 6 wherein the bottoms prior to step(c) is admixed with a coal tar pitch containing fraction in an amount toprovide a mixture in which no more than about 20 percent of thecomponents thereof boil above above about l200 F.

8. The process as defined in claim 6 wherein the fractionation zone isoperated at an overhead temperature from about 300 F. to about 400 F., abottoms temperature from about 650 F. to 850 F., a pressure from about25 p.s.i.g. to about 90 p.s.i.g. and a volumetric recycle ratio, basedon equivalent feed to the, fractionation'zone, from about 0.321 to about2.0:].

9. A delayed coking process for producing graphitizable needle cokecomprising:

a. introducing a feed containing coal tar pitch into a coker combinationfractionation zone operating under conditions to provide a heavy oilfraction having upper and lower cut points within the range from about600 F. to about l,000 F., said fraction having a high content ofcondensed ring aromatic compounds, and to flash material boiling at atemperature no greater than about l,000 F. from the feed;

b. recovering the heavy oil fraction from the combination fractionationzone;

c. passing at least a portion of the heavy oil fraction through aheating zone to effect heating thereof to a temperature from about 900F. to about l,000 F;

d. introducing the heated heavy oil fraction into a coke drum operatingat a temperature from about 840 F. to about 900 F. to effect delayedcoking thereof; and

e. recovering graphitizable needle coke from said coke drum.

[0. The process as defined in claim 9 wherein the heavy oil fractionprior to step (c) is admixed with a coal tar pitch containing fractionin an amount to provide a mixture in which no more than about 20 percentof the components thereof boil above about l,200 F.

11. A delayed coking process for producing graphitizable needle coke andcarbon grade coke from a feed containing coal tar pitch, comprising:

separating a feed containing coal tar pitch into a first fraction havingupper and lower cut points within the range from about 600 F. to aboutl,000 F. and a remaining heavier second fraction, both having a highcontent of a mixture of condensed ring aromatic compounds; rapidlyheating the first fraction to delayed coking temperature; subjecting thefirst fraction to delayed coking to produce graphitizable needle coke;and subjecting the remaining heavier second fraction to delayed cokingto produce carbon grade coke.

12. A delayed coking process for producing graphitizable needle coke andcarbon grade coke from a feed containing coal tar pitch, comprising:

a. introducing a feed containing coal tar pitch into a separation zoneto produce a first fraction having a boiling point of no greater thanabut l000 F. and a second heavier remaining fraction, each having a highcontent of a mixture of condensed ring aromatic compounds; b.introducing the first fraction into a fractionation zone operated underconditions to produce a bottoms having upper and lower cut points withinthe range from about 600 F. to about l,000 F.;

c. passing at least a portion of the bottoms through a heating zone toeffect heating thereof to a temperature from about 900 F. to about l,000F;

d. introducing the heated bottoms into a first coking drum to effectdelayed coking thereof at a temperature from about 840 F. to about 900F. to produce graphitizable needle coke;

e. passing overhead vapors from the first coking drum to thefractionation zone;

. introducing the remaining second fraction from the separation zoneinto a heating zone wherein the remaining second fraction is heated to atemperature from about 900 F. to about 960 F;

g. introducing the heated remaining second fraction into a second cokingdrum, operating at a temperature from about 840 F. to about 900 F. toeffect delayed coking thereof to carbon grade coke; and

h. passing overhead vapors from the second coking drum into saidfractionation zone.

13. A delayed coking process for producing graphitizable needle coke andcarbon grade coke from a feed containing coal tar pitch, comprising:

a. introducing a feed containing coal tar pitch into a coker combinationfractionation zone operating under conditions to provide a heavy oilfraction having upper and lower cut points within the range from about600 F. to about l,000 F., said fraction having a high content ofcondensed ring aromatic compounds, and to flash material boiling at atemperature no greater than about l,000 F. from the feed;

b. recovering the heavy oil fraction from the combination fractionationzone;

c. passing at least a portion of the heavy oil fraction through aheating zone to effect heating thereof to a temperature from about 900F. to about l,000 F.;

d. introducing the heated heavy oil fraction into a first coke drumoperating at a temperature from about 840 F. to about 900 F. to effectdelayed coking thereof to produce graphitizable needle coke;

e. introducing overhead vapors from the first coking drum into thecombination fractionation zone;

f. recovering the unfiashed portion of the feed from the combinationfractionation zone;

g. introducing said unflashed portion into a flash zone to flash anyremaining material boiling at a temperature no greater than about l,000F. therefrom, said flashed material being combined with the portion ofthe recovered heavy oil fraction which is to be heated;

h. heating the remaining liquid fraction from the flash zone to atemperature from about 900 F. to about 960 F.;

i. introducing the heated remaining liquid fraction into a second cokingdrum operated at a temperature between about 840 F. and about 900 F. toeffect delayed coking thereof to carbon grade coke; and

j. introducing overhead vapors from the second coking drum into thecombination fractionation zone.

2. The process as defined in claim 1 wherein the upper and lower cutpoints of the fraction fall within the range from about 600* F. to about1,200* F.
 3. The process as defined in claim 1 wherein the upper andlower cut points of the fraction fall within the range from about 600*F. to about 1,000* F.
 4. The process as defined in claim 1 wherein saidcoking is effected in a coke drum operating at an overhead temperaturebetween about 840* F. and about 900* F.
 5. The process as defined inclaim 4 wherein said coke drum is operated at a pressure from about 15to about 90 p.s.i.g.
 6. A delayed coking process for producinggraphitizable needle coke from a feed containing coal tar pitch,comprising: a. introducing a feed containing coal tar pitch into aseparation zone wherein a fraction having a boiling point of no greaterthan about 1,000* F. is separated from the feed, said fraction having ahigh content of condensed ring aromatic compounds; b. introducing thefraction into a fractionation zone operated under conditions to producea bottoms having upper and lower cut points within the range from about600* F. to about 1,000* F.; c. passing at least a portion of the bottomsthrough a heater to effect heating thereof to a temperature from about900* F. to about 1,000* F.; d. introducing the heated bottoms into acoking drum to effect delayed coking thereof at a temperature from about840* F. to about 900* F. to graphitizable needle coke; and e. passingoverhead vapors from the coking drum to the fractionation zone.
 7. Theprocess as defined in claim 6 wherein the bottoms prior to step (c) isadmixed with a coal tar pitch containing fraction in an amount toprovide a mixture in which no more than about 20 percent of thecomponents thereof boil above above about 1200* F.
 8. The process asdefined in claim 6 wherein the fractionation zone is operated at anoverhead temperature from about 300* F. to about 400* F., a bottomstemperature from about 650* F. to 850* F., a pressure from about 25p.s.i.g. to about 90 p.s.i.g. and a volumetric recycle ratio, based onequivalent feed to the fractionation zone, from about 0.3:1 to about2.0:1.
 9. A delayed coking process for producing graphitizable needlecoke comprising: a. introducing a feed containing coal tar pitch into acoker combination fractionation zone operating under conditions toprovide a heavy oil fraction having upper and lower cut points withinthe range from about 600* F. to about 1,000* F., said fraction having ahigh content of condensed ring aromatic compounds, and to flash materialboiling at a temperature no greater than about 1,000* F. from the feed;b. recovering the heavy oil fraction from the combination fractionationzone; c. passing at least a portion of the heavy oil fraction through aheating zone to effect heating thereof to a temperature from about 900*F. to about 1,000* F; d. introducing the heated heavy oil fraction intoa coke drum operating at a temperature from about 840* F. to about 900*F. to effect delayed coking thereof; and e. recovering graphitizableneedle coke from said coke drum.
 10. The process as defined in claim 9wherein the heavy oil fraction prior to step (c) is admixed with a coaltar pitch containing fraction in an amount to provide a mixture in whichno more than about 20 percent of the components thereof boil above about1,200* F.
 11. A delayed coking process for producing graphitizableneedle coke and carbon grade coke from a feed containing coal tar pitch,comprising: separating a feed containing coal tar pitch into a firstfraction having upper and lower cut points within the range from about600* F. to about 1,000* F. and a remaining heavier second fraction, bothhaving a high content of a mixture of condensed ring aromatic compounds;rapidly heating the first fraction to delayed coking temperature;subjecting the first fraction to delayed coking to produce graphitizableneedle coke; and subjecting the remaining heavier second fraction todelayed coking to produce carbon grade coke.
 12. A delayed cokingprocess for producing graphitizable needle coke and carbon grade cokefrom a feed containing coal tar pitch, comprising: a. introducing a feedcontaining coal tar pitch into a separation zone to produce a firstfraction having a boiling point of no greater than abut 1000* F. and asecond heavier remaining fraction, each having a high content of amixture of condensed ring aromatic compounds; b. introducing the firstfraction into a fractionation zone operated under conditions to producea bottoms having upper and lower cut points within the range from about600* F. to about 1,000* F.; c. passing at least a portion of the bottomsthrough a heating zone to effect heating thereof to a temperature fromabout 900* F. to about 1,000* F; d. introducing the heated bottoms intoa first coking drum to effect delayed coking thereof at a temperaturefrom about 840* F. to about 900* F. to produce graphitizable needlecoke; e. passing overhead vapors from the first coking drum to thefractionation zone; f. introducing the remaining second fraction fromthe separation zone into A heating zone wherein the remaining secondfraction is heated to a temperature from about 900* F. to about 960* F;g. introducing the heated remaining second fraction into a second cokingdrum, operating at a temperature from about 840* F. to about 900* F. toeffect delayed coking thereof to carbon grade coke; and h. passingoverhead vapors from the second coking drum into said fractionationzone.
 13. A delayed coking process for producing graphitizable needlecoke and carbon grade coke from a feed containing coal tar pitch,comprising: a. introducing a feed containing coal tar pitch into a cokercombination fractionation zone operating under conditions to provide aheavy oil fraction having upper and lower cut points within the rangefrom about 600* F. to about 1,000* F., said fraction having a highcontent of condensed ring aromatic compounds, and to flash materialboiling at a temperature no greater than about 1,000* F. from the feed;b. recovering the heavy oil fraction from the combination fractionationzone; c. passing at least a portion of the heavy oil fraction through aheating zone to effect heating thereof to a temperature from about 900*F. to about 1,000* F.; d. introducing the heated heavy oil fraction intoa first coke drum operating at a temperature from about 840* F. to about900* F. to effect delayed coking thereof to produce graphitizable needlecoke; e. introducing overhead vapors from the first coking drum into thecombination fractionation zone; f. recovering the unflashed portion ofthe feed from the combination fractionation zone; g. introducing saidunflashed portion into a flash zone to flash any remaining materialboiling at a temperature no greater than about 1,000* F. therefrom, saidflashed material being combined with the portion of the recovered heavyoil fraction which is to be heated; h. heating the remaining liquidfraction from the flash zone to a temperature from about 900* F. toabout 960* F.; i. introducing the heated remaining liquid fraction intoa second coking drum operated at a temperature between about 840* F. andabout 900* F. to effect delayed coking thereof to carbon grade coke; andj. introducing overhead vapors from the second coking drum into thecombination fractionation zone.